The interaction between cucuribit[8]uril (Q[8]) and as eries of 4-pyrrolidinopyridiniums alts bearing aliphatic substituents at the pyridiniumn itrogen, namely 4-(C 4 H 8 N)C 5 H 5 NRBr,w here R = Et (g1), n-butyl (g2), n-pentyl (g3), n-hexyl (g4), n-octyl (g5), n-dodecyl (g6), has been studied in aqueous solution by 1 HNMR spectroscopy,e lectronic absorption spectroscopy,i sothermal titrationc alorimetry and mass spectrometry.S ingle crystal X-ray diffraction revealed the structure of the host-guest complexes for g1, g2, g3, and g5. In each case, the Q[8] contains two guest molecules in ac entrosymmetric dimer.T he orientation of the guest molecule changes as the alkyl chain increases in length. Interestingly,i nt he solid state, the inclusion complexes identified are different from those observed in solution,a nd furthermore, in the case of g3, Q[8] exhibits two different interactions with the guest.I ns olution,t he length of the alkyl chain plays as ignificant role in determiningt he type of host-guest interaction present.[a] W.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.